Methylene blue (CI 52015) is a heterocyclic aromatic chemical compound with the molecu another histology stain, new methylene blue, nor with the methyl violets often used as pH indicators.
As an experimental pharmaceutical drug, the International Nonproprietary Name (INN) of methylene blue is methylthioninium chloride.[2][3]
Methylene blue was first prepared in 1876 by German chemist Heinrich Caro (1834-1910).[4]